Chronic lymphocytic leukemia (CLL) is the most common type of adult leukemia whose clinical outcome is predicted in great part by the IgV(H) gene mutational status. Patients with IgV(H) un-mutated status (40% of all patients at diagnosis) develop progressive disease at a median of 3 years and have inferior overall survival. In contrast, IgV(H) mutated patients (60% of all CLL patients at diagnosis) have a median progression time of 9.2 years, with some patients never requiring therapy. Reasons for adverse outcome in IgV(H) un-mutated disease include in part a high predisposition to clonal evolution. Identification of initiation and progression events in IgV(H) un-mutated patients offers the potential to substantially improve risk stratification and also to identify novel targets crucial to initiation and progression for which new therapies can be developed. To identify novel initiating and progression events in CLL, our research groups together have employed two novel strategies. The first combines DNA methylation analysis with genetic studies of familial predisposition. This work demonstrated down-regulation by DNA methylation of the pro-apoptotic gene DAPK1. This event not only is a general characteristic of human CLL but also is associated with familial predisposition to developing CLL. We also have used the TCL1 transgenic mouse model of CLL that mimics IgV(H) un-mutated human CLL to identify additional molecular events involved in CLL initiation or progression. Molecular events identified in murine CLL were confirmed to also occur in human CLL. We now propose to expand our findings relative to these initiation and progression events through both a translational laboratory aim, focused on DAPK1 in CLL, and a clinical aim, focused on improving risk stratification in IgV(H) un-mutated CLL as part of a large North American Intergroup Phase III trial. Our specific aims are to determine: 1) the importance of DAPK-mediated apoptosis in B-cells, frequency of allele-specific expression in CLL, and mechanisms by which DAPK1 gene expression is regulated in B- cells, with particular focus on regulators potentially relevant to B-cell transformation to CLL; and 2) the significance of baseline and serial molecular events in CLL initiation or progression on progression-free survival and clonal evolution in newly diagnosed CLL patients with IgV(H) un-mutated disease. Our overall hypothesis in this proposal is that improved understanding of initiating and progression events in CLL will lead to more effective risk stratified approaches for IgV(H) un-mutated CLL, and also novel targets for which therapies can be developed to potentially prevent clonal evolution or progression of this disease. RELEVANCE (See instructions): This SPORE translational project performs detailed study of the CLL initiating gene DAPK1 and assesses the impact of select molecular events on treatment free survival and clonal evolution in newly diagnosed IgV(H) un-mutated patients. These findings may improve risk of progression of IgV(H) un-mutated CLL patients and also identify novel targets for targeted therapies to prevent clonal evolution or progression of this disease.